1. Field of the Invention
The invention relates in general to a processing method for image scanning, and more particularly, the invention relates to a method for enhancing scan resolution.
2. Description of the Related Art
Image conversion apparatus, including copy machines, fax machines, and scanners, convert a visual image into a certain electronic form to allow printing, storing, transmission or other functions. Such an apparatus uses an optical sensor such as a charge coupled device (CCD) or contact image sensor (CIS) is used for image detection. For a color display, the common structure of the optical sensor is formed of red, green and blue CCD devices. All the CCD devices are exposed for a certain period of time. The sensed charges are then delivered to the analog shifter buffer for the subsequent processes.
Typically, to enhance the resolution, the forwarding distance of the optical sensor is reduced for each scan, so that more image data are obtained. Consequently, the size of the detecting cell in the optical sensor cannot be varied, and the brightness obtained by the optical sensor is an average of brightness for several points. To enhance the resolution obtained by this method, the performance of the scanner in modulation transfer function (MTF) is deteriorated.